Today in 1941, John Mauchly visited John Atanasoff at Iowa State University. During the next five days he learned everything he could about what became to be known as the Atanasoff-Berry Computer (ABC) which he first heard about when Atanasoff visited Philadelphia in December 1940. The ABC was the first electronic digital computing device but was never put to actual use because both Atanasoff and Berry left Iowa in 1942 to contribute to the war effort and did not resume the work after the war. The significance of this meeting emerged years later when it became part of the evidence that led the judge in the case of Honeywell, Inc. v. Sperry Rand Corp., et al.to decide that the ENIAC patent was invalid, among other reasons, because “Eckert and Mauchly did not themselves invent the automatic electronic computer, but instead derived that subject matter from one Dr. John Vincent Atanasoff.”

Campbell-Kelly and Aspray conclude in Computer: A History of the Information Machine: “The extent to which Mauchly drew on Atanasoff’s ideas remains unknown, and the evidence is massive and conflicting. The ABC was quite modest technology, and it was not fully implemented. At the very least we can infer that Mauchly saw the potential significance of the ABC and that this may have led him to propose a similar electronic solution to the Ballistic Research Laboratory [at the Moore School of Electrical Engineering at the University of Pennsylvania] computing needs.”

They also note that in June 1941, Mauchly and Atanasoff “parted on very amicable terms.” Indeed, Mauchly wrote to Atanasoff on September 30th of that year: “A number of different ideas have come to me recently anent computing circuits—some of which are more or less hybrids, combining your methods with other things, and some of which are nothing like your machine. The question in my mind is this: is there any objection, from your point of view, to my building some sort of computer which incorporates some of the features of your machine? … Ultimately a second question might come up, of course, and that is, in the event that your present design were to hold the field against all challengers, and I got the Moore School interested in having something of the sort, would the way be open for us to build an ‘Atanasoff Calculator’ (a la Bush analyzer) here?”